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March, 1932

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The royalties owned by the Hartley Main Collieries Limited, which are now 13,233 acres in extent, were originally operated by two separate concerns, the Seaton Delaval Coal Company and the Cramlington Coal Company, these being amalgamated to form the present company in May, 1929.

Towards the end of 1930 Mr. C. A. Nelson, a well known mining engineer, was appointed Chairman and Managing Director of the Hartley Main Collieries Limited, and Mr. J. A. Metcalf was appointed Chief Engineer of the company. A policy of modernisation and re-equipment was immediately commenced. This included the electrification of the whole of the company's collieries, which comprise the Hartford, Shankhouse, Cramlington Ann, West Cramlington, Dudley, New Delaval, Seaton Delaval and Hartley pits, and the bringing up to date of screening plant and transport facilities. Since August, 1930, the first five of the pits mentioned have been completely electrified both above and below ground, making it possible to shut clown no fewer than 15 compressors and 37 boilers. By the time the electrification of the remaining collieries s completed it will have been possible to shut down a further eleven boilers. No less than six electric winders have been put into commission in 14 months, and a further three are being constructed.

At Seaton Delaval are centralised engineering shops, locomotive repair shops and wagon shops. Views in the engineering shops are given in Figs. 5 and 6, and show a haulage and winder in course of conversion to electric drive. Many of these conversions from steam and compressed air have been made as an incidental to the reconstruction scheme, the whole of the work having been carried out in the company's own shops, which are fully equipped with modern machine tools.

In modernising the screening plants, particular attention has been given to avoiding breakage of the coal, and at Hartley, for instance, where a new plant has been erected, one of the most complete anti-breakage systems that we have yet seen has been incorporated.

Underground, the object of the modernisation has been to convert the equipment from compressed air (and even steam) to electric drive, and to mechanise as far as possible the coal-winning operations. In effecting this, every effort has been made to concentrate the workings, and in many cases haulages have been eliminated, and the pumping plant centralised. Over 22,000 yards of power cable have been put into commission during the last year and nearly 7,000 electrical H.P. added to the equipment.

The whole of the electric energy is derived from the mains of the Newcastle Electric Supply Company, feeders at 11,000 and 20,000 volts being led to the various pits. In some cases the current is transmitted by the company's own lines, a substation being provided at each pit. Generally the inter-pit transmission is effected at 2,750 volts, the current being stepped down to 440 volts for use in the various motors under 50 H.P. and to 110 volts for lighting.

To make our story complete we propose to deal with each colliery in turn and give an outline of the work that has been accomplished in each case. The relative position of the collieries is shown in the accompanying sketch map (Fig. 3), which also shows the company's private railway lines connecting the pits to the Northumberland docks on the Tyne. A new staith is being erected at the west end of these docks, the arrangements being such that ships up to any tonnage can be loaded at a rate of up to 1,000 tons per hour. These facilities, of which more will be said later, have been erected by the Tyne Improvement Commission, after somewhat protracted negotiations, with a prior right of use for the Hartley Main Collieries Limited.

Hartley Colliery.

The most outstanding improvement at the Hartley pit is the new screening plant. This has replaced a cumbersome battery of rather ancient gravity bar-screens, fed by kick-up tipplers, which were very extravagant as regards labour. Views of the old plant are given in Figs. 1 and 2, and the somewhat brutal treatment that was obviously meted out to the coal with this equipment contrasts strongly with the care that is taken to avoid breakage in the new. In this, excepting only the short passage of the coal over the actual screen meshes, the whole of the handling is effected by rubber belt conveyors.

Owing to the fact that the new screens had to be erected without interfering with the old plant, the layout presented certain difficulties, and the design had to be modified to some extent to meet the exigencies of the site. Drawings showing the general layout and construction are reproduced in Fig. 4. Two tippler units are provided, but provision is made for a third to he added at a later date. The rubber picking hands are 4 ft. 6 in. wide, and, in order to distribute the coal evenly, adjustable feeders are provided immediately beneath the tippler hoppers, causing a steady stream of uniform thickness to spread over the mesh-plates. This not only facilitates picking but also improves the screening results. Any small produced during the travel is eliminated by a further screen fitted above the jib ends. The jibs also are provided with rubber bands, the end drums which descend into the wagons being of small diameter in order to reduce the height of free fall of the coal to the minimum. A lowering jib is not, of course, provided in the case of the small-coal belt. Since the small coal is removed in the main screening operation, a check can be made on any tub containing other than small, and an excessive quantity of stone readily detected.

Scraper conveyors are arranged to carry the stones and brasses to their respective loading points, whence they are removed by railway wagons or alternatively to a skip-hoist. The tub circulating system is entirely automatic, the tubs gravitating to a creeper which elevates them to a sufficient height to enable them to gravitate to the tipplers and thence back to the shaft.

A notable innovation in connection with the actual coal-winning operations at these pits is the experiment with the "Cardox" plant which has been installed. This is a non-explosive agent for bringing down coal, the principle being that a charge of liquid CO2, contained in a special steel cartridge, is gasified by a "heater element." It is claimed that the temperature created is not sufficient to initiate a firedamp or coal-dust explosion, while the gas released — carbon dioxide — is in itself a fire retardant. Its rapid expansion, moreover, produces an intense cold which further reduces the possibility of an explosion being initiated. The disruptive effort is stated by the inventor to be only one-third of that developed by black powder, and one-eighth of that developed by permitted explosives.

The improvements at Hartley have also been extended to the other underground plant, which has been totally electrified. The haulages have been converted from compressed-air drive and a complete system of machine mining introduced. The seam worked is the Low Main, which is a high quality steam coal, having a section of 1 ft. 10 in. It is overlain by 6 in. of band, which is removed with the seam, the roof proper consisting of strong post. The Low Main was worked in the closing years of the last century, but was abandoned in 1897 until a year or two ago. In the reopening out operations considerable trouble was given by water percolating through from the old goafs in the Yard Seam above, but four longwall faces were eventually won out in the South District and are now producing 360 tons per day As far as possible the faces are maintained at 80 yards in length, and are undercut by Jeffrey-Diamond "BR." machines, which make a kirve, 5 ft. in depth and 4½ in. in height, in the bottom of the seam. These work in conjunction with Eickhoff shaker conveyors (MT. 15) on the face and Blackett chain conveyors in the gate roads. Motors of 17 B.H.P. operate the face units and 12-H.P. motors the gate conveyors; in both cases these motors were supplied by Bruce, Peebles & Co. Ltd. They are of the flameproof type, specially designed for use underground, and are provided with ball bearings throughout.

The power supply is carried down to a substation at the shaft bottom at 3,000 volts, where it is stepped down to 440 volts in 100-kVA. transformer. Part of this supply is utilised by an endless hauler driven by a 25-H.P. motor and a further H.T. cable carries the current to the inbye substation at 3,000 volts. Each set of coalcutters, drills and conveyors is served by a Metrovick three-panel switchboard. The coalcutters are remote controlled from gate-end boxes, which are served from appropriate panels on the switchboard.

Four-inch by four-inch S. F. steel props, supplied by Hugh Wood & Co. Ltd., are in use on all the faces and have given very excellent service indeed. They are set with wood lids one inch thick.

Hartford Colliery.

At this colliery, also, the screening plant has been modernised, an old type of jigger having been replaced by equipment supplied by the Sunderland Forge Co. Ltd. This consists of an "all-mechanical" vibratory screen having a capacity of 60 tons per hour, a view of the plant being reproduced in Fig. 7. With this screen the motion is imparted by connecting the vibrator to a steel strip fastened to the mesh, it being possible to vary the intensity of vibration while the screen is in motion. The inclination of the screen can also be readily varied, and it is claimed that a true wire-vibration is secured. The vibrating mechanism may be driven by belt, chain or motor, the final alternative having been adopted in the present case. A one-inch mesh screen is fitted, the undersize passing on to a rubber conveyor and into a truck, and the oversize on to a picking belt, then it is rescreened.

The tensioning arrangements for the wire mesh of this screen are particularly interesting. It is possible, by manipulating the easily accessible handwheels at the side, to put a variable tension on to the wires, and it is claimed that by tensioning the receiving end slightly less than the discharge end the material is at first more vigorously treated owing to the greater amplitude of the lesser tensioned wires. A preliminary coarse grading is thus rapidly effected at the upper end of the screen, while the more difficult and near-sized particles are subjected to gentler and finer treatment as they approach the more highly tensioned wires at the discharge end

The winding equipment at this pit has also been brought up to date, electric plant having been erected. This consists of an 8-ft. diameter parallel drum operated by a 193-H.P. 2,750-volt induction motor, replacing an old steam-driven unit. A point of interest in connection with this plant is that it was put to work in the same engine house as the steam winder, within a period of 14 days. During this time the coal drawing at the company's other pits was augmented so that no loss of output took place. That this work should have involved an interruption in coal drawing of only 14 days, particularly as considerable alteration had to be made to the foundations, testifies to the capacity of the engineering staff for getting things done.

Shankhouse and Cramlington Ann Pits.

The winding arrangements at this pit have also been modernised. Formerly an old vertical steam plant undertook the winding duty here, but has now been replaced by electrical equipment. A view of the new winder is given in Fig. 9, and it is of some interest to know that it was originally a main-and-tail hauler which was converted in the colliery shops to serve its present purpose. The change-over was made without any interruption of coal drawing, the new equipment being erected behind the old winder house on a site previously occupied by the blacksmiths' shops. The two drums are 5 ft. 6 in. in diameter and are driven by a 120-H.P. 2,750-volt induction motor supplied by J. H. Holmes & Co. Ltd., the equipment being capable of raising up to 900 tons a day from a depth of 213 ft.

Here it has been sufficient to modify the existing screens without doing much re-equipment work. New tipplers have, however, been added to reduce labour costs, and the chutes rearranged to minimise breakage. Lowering jibs have been added with the same object.

Similar alterations have been made to the screens at the Cramlington Ann Pit. These were formerly operated by three steam engines, and the drive has now been split up among six electric motors. New tipplers have been provided, but the original shakers have not been modified. The winding arrangements at this pit have also been modernised, an old vertical steam winder having been replaced by electrical equipment. Here again the mechanical parts are a product of the colliery shops, the drive being provided by a 175-H.P. motor by the Metropolitan-Vickers Electrical Co. Ltd. This equipment is housed in a steel-framework building, with a 4½-in. brick filling, erected by the colliery company themselves.

The Dicky pit at this colliery has now been attached to the Ann pit as part of the reorganisation scheme. Coal is brought up the Dicky shaft from the Low Main seam and raised to the Main Coal level, the tubs subsequently being hauled to the Ann pit bottom. By concentrating the output on the Ann pit in this way it has been possible to dismantle much of the plant at the Dicky pit, and more economic working has been secured. An electric winder — a further product of the colliery shops — driven by a 90-H.P. J. H. Holmes & Co. Ltd. motor has been erected at the Dicky pit to supersede the old steam equipment.

West Cramlington Colliery.

The winder at the No. 1 pit of this colliery has also been electrified, and the steam plant dismantled. Although the electrical equipment has been erected in the same house as the old steam plant the change-over was effected without any interruption to coal drawing. This winder is also a converted main-and-tail haulage, a 100-H.P. J. H. Holmes & Co. Ltd. motor having been provided to take the drive. Such were the dimensions of the winding house that a small annexe had to be built on one side to accommodate the motor, this, of course, having been erected in readiness before the actual change-over was accomplished.

The screening plant at this colliery has been entirely shut down, the coal being transported at the surface to the central plant at the Ann pit by two petrol locomotives. The locomotives (Fig. 8) are of 2-ft. 4-in. gauge and haul the pit tubs in trains of 21, the journey of 1¼ miles being accomplished in six minutes. At the end of the journey the tubs are shunted up an incline, nine at a time, and raised to the tippler level of the central screening plant.

(To be continued.)

Drawings and Photographs accompanying the article